Domestic infestation by Sclerodermus sp. with associated skin manifestation^*

Abstract:

Sclerodermus sp. is an aculeate insect (Hymenoptera: Bethylidae), measuring 2-4 mm in length. It is a parasitoid and needs termites as hosts to complete its life cycle. It is found in a wide variety of woods and may accidentally sting humans who come near affected wooden objects. A 50-year-old woman presented two episodes of intense pruritic lesions. Clinical diagnosis of insect bite was doubtful since there were no pets at home, lesions had not started during summer and the patient denied rural activities. During a night episode of itching, the patient examined her bed and found 8 insects likely to be responsible for the bites. Scanning electron microscopy revealed typical features of a female of the genus (wingless and with multiple stingers at the lower end of the abdomen).

Keywords:
Insects bites and stings; Microscopy, electron, scanning; Skin diseases

INTRODUCTION

The genus Sclerodermus (Hymenoptera, Bethylidae) has a worldwide distribution and comprises 80 described species. They are small wasps, measuring 2-4 mm, and vary in color from light to dark brown. There are apterous, micropterous and macropterous species.¹ They are idiobiont ectoparasitoids that feed on the larvae of xylophagous insects of the order Coleoptera (termites) that live in wood. The wasps find hosts by entering pre-existing galleries in the wood. They then feed on the larval hemolymph and lay eggs on the surface of the hosts, which are paralyzed by venom but remain alive, using them as a source of food.^2,3

The females may inject venom into humans that live in or come into contact with infested houses or furniture.

CASE REPORT

A 50-year-old woman presented with intense pruritic edematous lesions suggestive of insect bites and responded well to systemic prednisone therapy (Figure 1). Two months later, she presented a relapse, which was controlled by topical corticosteroid therapy with betamethasone.

Figure 1
Erythematous edematous lesions

Clinical diagnosis of insect bite was doubtful, since the patient did not have pets at home, the lesions had not appeared during summer, and she denied activities in a rural area. During a night episode of itching, the patient examined her bed and found eight insects of 2 mm in length (Figure 2). Subsequently, she identified the insects in the ceiling lamp hanging above the bed.

Figure 2
Insects measuring 2 mm

The collected specimens, likely to be responsible for the bites, were examined with scanning electron microscopy (SEM), showing the typical wingless aspect of the females of the genus (Figure 3). The examination of the lower end of the abdomen identified multiple stingers (Figure 4).

Figure 3
Scanning electron microscopy. general view of a small, wingless wasp (x60)

Figure 4
Scanning electron microscopy. Detail of the multiple abdominal stingers (x1600)

DISCUSSION

Sclerodermus sp. may accidentally sting humans who come near affected wooden objects. The main reports are from Italy^4-6 and Spain,⁷ and, more recently, 3 cases were reported in Latin America, namely Costa Rica.⁸

Exposure to old wood furniture is a risk factor. A report of Sclerodermus stings in Italy described 9 affected individuals, 7 of them working with antiques, and 2 housewives. In all cases furniture or household dust were the source of environmental contamination. ⁵

Some authors suggest that the skin lesions caused by Sclerodermus sp may be considered as an occupational disease for restorers, antique dealers, and those working with wooden products.^6,9

These insects sting the host larvae of wood borers, injecting their venom to paralyze them. The stinger identified by SEM is used for that purpose and is probably the cause of intense skin reactions. There have been reports of associated systemic symptoms such as discomfort and fever.

No cases of stings from Sclerodermus sp. have been reported in Southern Brazil, but new cases of this insect sting may emerge, and dermatologists should be aware of this possibility.

• *
  Work conducted at the Dermatology Alliance, Universidade Federal de Pelotas, Pelotas (RS), Brazil.
• Financial support: None.

REFERENCES

• ¹
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• ⁸
  Jirón LF, Hanson P, Zeledón R. An outbreak of dermatitis produced by the stings of Sclerodermus sp. (Hymenoptera, Bethylidae) in Costa Rica. Central America. Acta méd costarric 2016;58:122-125.
• ⁹
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Publication Dates

• Publication in this collection
  Jul-Aug 2018

History

• Received
  17 Aug 2017
• Accepted
  13 Dec 2017